The present invention relates to a liquid crystal apparatus. More particularly, the invention relates to a smectic liquid crystal apparatus, in particular to the configuration of such an apparatus and a method of driving the same wherein optimum drive voltage values are obtained automatically and the apparatus is driven with the thus obtained voltage values.
Research into and development of liquid crystal panels has been conducted actively in recent years because of their potential to be able to provide display quality comparable to that of CRTs despite their thin, light-weight, and compact construction. Nowadays, liquid crystal panels are used not only for television sets and computer monitors but also for so-called spatial light modulators such as optical shutters.
In liquid crystal materials used in liquid crystal panels, the threshold voltage at which the liquid crystal molecules switch from one state to another has temperature dependency. Furthermore, liquid crystal panels have viewing-angle dependency in that the visibility of the display varies depending on the viewing angle. Accordingly, liquid crystal apparatuses have usually been equipped with a device for adjusting the voltage applied to the liquid crystal so that optimum display can be produced in operation, and it has been practiced to adjust the voltage for optimum display while actually viewing the liquid crystal screen.
However, when using a liquid crystal panel as a spatial light modulator, since the liquid crystal panel is mounted inside the apparatus, the display condition of the liquid crystal panel cannot be checked directly by the human eye. In view of this, an object of the present invention is to provide a liquid crystal apparatus incorporating a configuration for automatically obtaining the drive voltage value necessary to drive the liquid crystal panel in an optimum display condition (i.e., the highest contrast condition) when the display condition of the liquid crystal panel cannot be checked directly by the human eye (such a drive voltage value is hereinafter referred to as the xe2x80x9coptimum drive voltage valuexe2x80x9d).
The liquid crystal apparatus of the present invention is used, among others, for a display apparatus or for a spatial light modulator used to adjust the light amount of a two-dimensional optical signal at very high speed. When the liquid crystal apparatus of the invention is used as a spatial light modulator, the liquid crystal panel acts as an optical shutter for forming the incident two-dimensional optical signal into an output light beam of a prescribed state.
The present invention is directed to a liquid crystal apparatus using a smectic liquid crystal such as a ferroelectric liquid crystal or an antiferroelectric liquid crystal.
To achieve the above object, the present invention provides the following configuration.
The liquid crystal apparatus of the present invention comprises: a liquid crystal panel constructed by sandwiching a smectic liquid crystal between a pair of substrates; a display capture device for capturing an image displayed on the liquid crystal panel; a capture memory for storing the captured image data; a reference memory for storing reference image data; a display difference circuit which compares the data stored in the capture memory with the data stored in the reference memory; a voltage value adjusting circuit for adjusting a voltage value for application to the liquid crystal panel; and an optimum voltage setting means.
The liquid crystal apparatus of the present invention also comprises a liquid crystal panel constructed by sandwiching a smectic liquid crystal between a pair of substrates respectively having a plurality of signal electrodes and scanning electrodes. In this configuration, the signal voltage to be applied to the signal electrodes and the scanning voltage to be applied to the scanning electrodes are respectively varied and, in each combination of the signal voltage and the scanning voltage, the display produced on the liquid crystal panel is captured by the display capture device. The captured image data is stored in the capture memory, and the thus captured image data is compared with the reference image data. Then, any combination of the signal voltage and the scanning voltage where the two data coincide is plotted as a coordinate point with the signal voltage along X axis and the scanning voltage along Y axis. The signal voltage value and scanning voltage value corresponding to the coordinates of the centroid of the region described by the plotted points are respectively set as the optimum drive voltage values.
Further, at the highest temperature and the lowest temperature in a temperature range where the liquid crystal apparatus is capable of operating, the same sequence of operations as described above is performed to obtain respectively plotted regions. The signal voltage value and scanning voltage value corresponding to the coordinates of the centroid of a region where the region described by the plotted points at the highest temperature overlaps the region described by the plotted points at the lowest temperature are respectively set as the optimum drive voltage values.
Using the liquid crystal apparatus of the present invention, optimum drive voltages can be set even when the display condition of the liquid crystal panel cannot be observed directly by the human eye. Further, by using the optimum drive voltages obtained by the above method, optimum display can be produced without having to adjust the drive voltages even if there occurs some degree of variation in the threshold voltage or the like of the liquid crystal due to temperature changes, etc.